Merge pull request matplotlib#28787 from meeseeksmachine/auto-backport-of-pr-28706-on-v3.9.x

Backport PR matplotlib#28706 on branch v3.9.x (Add Returns info to to_jshtml docstring)

Author: ksunden

lib/matplotlib/animation.py

@@ -1311,6 +1311,12 @@ def to_jshtml(self, fps=None, embed_frames=True, default_mode=None):
             What to do when the animation ends. Must be one of ``{'loop',
             'once', 'reflect'}``. Defaults to ``'loop'`` if the *repeat*
             parameter is True, otherwise ``'once'``.
+
+        Returns
+        -------
+        str
+            An HTML representation of the animation embedded as a js object as
+            produced with the `.HTMLWriter`.
         """
         if fps is None and hasattr(self, '_interval'):
             # Convert interval in ms to frames per second